MS44-P07 Structural Properties of (Ce,La)Pd2Al2-xGax Compounds Petr Doležal (Department of Condensed Matter Physics, Faculty of Mathematics and Physics, Charles University, Prague, Czech Republic) Dominik Kriegner (Department of Condensed Matter Physics, Faculty of Mathematics and Physics, Charles University, Prague, Czech Republic) Milan Klicpera (Department of Condensed Matter Physics, Faculty of Mathematics and Physics, Charles University, Prague, Czech Republic) Alexandra Rudajevová (Department of Condensed Matter Physics, Faculty of Mathematics and Physics, Charles University, Prague, Czech Republic) Jiří Prchal (Department of Condensed Matter Physics, Faculty of Mathematics and Physics, Charles University, Prague, Czech Republic) Pavel Javorský (Department of Condensed Matter Physics, Faculty of Mathematics and Physics, Charles University, Prague, Czech Republic)email: petr284@seznam.cz(Ce,La)Pd2(Al,Ga)2 are intermetallic compounds with a tetragonal CaBe2Ge2 structure type at room temperature. This structural type is very common in intermetallic compounds with a 1:2:2 stoichiometry. The studied compounds undergo a structural phase transition at low temperatures. The low temperature structure of CePd2Al2 is orthorhombic (Cmme) below 13.5 K [1] and CePd2Ga2 is triclinic below 125 K [2]. Similar structural behaviour is observed in their non-magnetic La analogues. It is not known what causes the different behaviour of CePd2Al2 and CePd2Ga2 compounds at low temperatures considering the room temperature structure is similar for both compounds. The CePd2Al2 is also one of the rare examples of Ce-based compounds whose magnetic excitations in crystal electric field does not fulfil the scheme based on a tetragonal point symmetry of the Ce ion [1].

In the presented study we focus in more detail on the structural properties of the (Ce,La)Pd2Al2-xGax series using the low temperature X-ray powder diffraction. These results are also compared with inelastic neutron spectra, which shows the behaviour of magnetic excitations in this series.  We found that specific Ga concentration leads to the suppression of the transition temperature in the CePd2Al2-xGax series. We also studied the structural transition on CePd2Al2 and LaPd2Al2 single crystals which were prepared by using the Czochralski method.
References:

[1] Chapon L. C. & Goremychkin E. A. & Osborn R. & Rainford B. D. & Short S. (2006). Physica B. 378-380. 819-820.

[2] Kitagawa J. & Ishikawa M. (1999). Journal of the Physical Society of Japan. 68. 2380-2383.
Keywords: low temperature structure, structural phase transition